Hi there.
I'm having some little problems during gameplay specially on Tomb Raider Legend, i'm running it at Next Generation mode, Underworld does the same aswell. Some slow down performance here and there, brakes... I had a lot of them before I formatted my pc, but still some of them decided to say to bugg me just a little more.
I find no reason for it to do this since I think I have a good graphics card, maybe it's the CPU's fault, which is Dual Core 3.40Ghz. Or RAM Memory ?

During the game, I turn the internet off, any programs not in usage, anti-virus. I have the lastest drivers too. I don't have a sold out version of TRL but I bought this one last year so I think it came with the latest patches since one time I wouldn't let me update to 1.2 because it was already installed.

Registry Settings
Full Install - True
Version 258
Language - English
EAXSupport Disabled
Disable 32Bit Textures......... Off
Disable Driver Management...... Off
Disable Dynamic Textures....... On
Disable Hardware DXTC.......... Off
Disable Hardware Shadow Maps... Off
Disable Hardware VP............ Off
Disable Non Pow2 Textures...... Off
Disable Null Render Targets.... Off
Dont Defer Shader Creation..... Off
Enable Depth Of Field.......... On
Enable FSAA.................... On
Enable Full screen Effects..... On
EnableReflection............... On
Enable Shadows................. On
Enable VSync................... Off
Enable Water FX................ On
Full screen.................... On
UseD3DFPUPreserve.............. Off
Use Low Res Depth Of Field..... Off
Use Ref Device................. Off
Use Shader20................... On
Use Shader30................... On

Registry Settings
Full Install - True
Version 256
Language - English
EAXSupport Disabled
Combat Mode.................... Manual
Disable 32Bit Textures......... Off
Disable Driver Management...... Off
Disable Dynamic Textures....... On
Disable Hardware DXTC.......... Off
Disable Hardware Shadow Maps... Off
Disable Hardware VP............ Off
Disable Non Pow2 Textures...... Off
Disable Null Render Targets.... Off
Dont Defer Shader Creation..... Off
Enable Depth Of Field.......... On
Enable Full screen Effects..... On
EnableReflection............... On
Enable Shadows................. On
Enable VSync................... On
Enable Water FX................ On
Full screen.................... On
UseD3DFPUPreserve.............. Off
Use Low Res Depth Of Field..... Off
Use Ref Device................. Off
Use Shader20................... Off
Use Shader30................... On

I used to have this message after completing Croft Manor after Bolivia or Peru or Japan....All because of Croft Manor. However I recently discovered that turning Next Generation Content off kills this bug, then turning it on again during the next level :) It's kinda weird tough.